Day Length Calculator
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Current Local Time
—This day length calculator shows the total hours and minutes of daylight between sunrise and sunset for any location and date.
What Is Day Length?
Day length is the total duration of sunlight between sunrise and sunset at a given location on a specific date. It is determined by your latitude, the Earth's axial tilt, and the planet's orbital position around the sun. At the equator, day length stays close to 12 hours year-round, while high-latitude regions experience dramatic swings — from 24 hours of sunlight during the summer solstice to just a few hours in winter.
The variation is extreme: near the Arctic Circle, day length can swing by 17+ hours between solstices, while at the equator it varies by only about 15 minutes all year. This calculator computes the exact hours and minutes of daylight for any location and date, factoring in atmospheric refraction that extends visible daylight by several minutes beyond the geometric sunrise-sunset window.
How Our Day Length Calculator Works
Our day length calculator computes the exact duration between calculated sunrise and sunset times for any latitude, longitude, and calendar date using the SunCalc library and Jean Meeus algorithms. It applies standard atmospheric refraction of 0.833° and runs entirely in your browser.
The tool first determines the precise sunrise and sunset times for your coordinates and date, then calculates the difference to deliver day length in hours and minutes, accurate to within seconds of observational data. No data is sent to any server — the entire computation is local and instant.
FAQ — Day Length Calculator
How many hours of daylight do I have today?
Enter your city or coordinates into the calculator above to get today's exact day length. In my experience, the results are accurate to within seconds. If you want to compare seasons, try entering the same location with different dates — the summer solstice (June 20-21) gives the longest day, and the winter solstice (December 21-22) gives the shortest.
Which location has the longest day length on Earth?
Locations inside the Arctic or Antarctic Circle experience 24-hour daylight during their respective summer solstices — the phenomenon known as midnight sun. Outside the polar circles, the longest day lengths occur at the highest latitudes: Reykjavik, Iceland (64°N) gets nearly 21 hours of daylight in June, while Tromsø, Norway (69°N) gets 24 hours.
Does day length include twilight hours?
No — day length measures only the time between astronomical sunrise and astronomical sunset (with refraction correction). Twilight adds usable light before sunrise and after sunset: civil twilight (sun 0-6° below horizon) extends usable daylight by about 20-30 minutes on each end. For practical purposes, your usable light is significantly longer than the calculated day length.
Why does day length matter for agriculture?
Many crops respond to photoperiod — the ratio of light to dark in a 24-hour cycle. Short-day plants (like rice and cotton) flower when days get shorter, while long-day plants (like wheat and spinach) flower when days get longer. Farmers use day length data to time planting and harvesting for optimal yields. The calculator helps track these critical photoperiod thresholds.
How does day length affect mood and sleep?
Shorter day length is strongly linked to seasonal affective disorder (SAD) and disrupted circadian rhythms. I've noticed that as days shorten in autumn, my sleep quality changes and I need more morning light exposure. Light therapy timed to sunrise — which you can calculate with our sunrise tool — is a proven treatment for SAD and helps regulate melatonin production.